2-Benzimidazolecarbamic acid esters by the cyanamide process

Abstract

A process for making 2-benzimidazolecarbamic acid, alkyl esters by reacting cyanamide or a cyanamide salt with an alkyl chloroformate in a weakly acidic to basic medium at a temperature between 0° and 105° C. to form an alkyl cyanocarbamate salt; then reacting the alkyl cyanocarbamate salt with an o-phenylenediamine in an acidic medium at a temperature between 40° and 130° C. to form the desired product and recovering it from the reaction mixture. The 2-benzimidazolecarbamic acid, alkyl esters are useful as fungicides and also useful as intermediates in the preparation of dialkyl esters of 2-carboxyaminobenzimidazole-1-carboxylic acids.

We claim: 
     
       1. A process for making a 2-benzimidazolecarbamic acid ester comprising reacting an alkyl cyanocarbamate of the following formula:   HN(CN)CO.sub.2 R     where   R is alkyl of 1 through 4 carbon atoms; with an o-phenylenediamine of the following formula: ##STR25## where X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; in the presence of water and sufficient acid to maintain a pH of from 2.5 to 5, until the precipitation of the 2-benzimidazolecarbamic acid ester is complete, and recovering said 2-benzimidazolecarbamic acid ester from the reaction mixture.   
     
     
       2. The process of claim 1 at a temperature from 40° to 130° C. 
     
     
       3. In the process for making a 2-benzimidazolecarbamic acid ester of the formula: ##STR26## wherein R is alkyl of 1 through 4 carbon atoms; X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; wherein cyanamide is reacted with an alkyl chloroformate of the formula ClCOOR where R is alkyl of 1 through 4 carbon atoms to form the corresponding alkyl cyanocarbamate salt and said alkyl cyanocarbamate salt is reacted with an o-phenylenediamine of the following formula: ##STR27## wherein X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; to produce the desired 2-benzimidazolecarbamic acid ester, the improvements comprising reacting the alkyl chloroformate and cyanamide in a weakly acidic to basic medium and reacting the alkyl cyanocarbamate salt and said o-phenylenediamine in the presence of water and sufficient acid to maintain a pH of 2.5 to 5.   
     
     
       4. The process of claim 3 when cyanamide is reacted with the alkyl chloroformate at a temperature between 0° and 105° C. and the alkyl cyanocarbamate salt and o-phenylenediamine are reacted at a temperature of 40° to 130° C. 
     
     
       5. The process of claim 3 wherein the reactants are present in the following mole equivalents:   ______________________________________                                    
o-phenylenediamine  1 mole                                                
alkyl chloroformate 1 - 3 moles                                           
cyanamide           1 - 3 moles                                           
______________________________________                                    
     
     
     
       6. A process such as set forth in claim 3 wherein the alkyl cyanocarbamate salt is separated from the reaction mixture prior to being reacted with the o-phenylenediamine. 
     
     
       7. A process for making a 2-benzimidazolecarbamic acid ester comprising reacting an alkyl cyanocarbamate salt of the following formula:   M[N(CN)CO.sub.2 R].sub.m     where   M is an alkali metal or an alkaline earth metal;   m is the valence of M; and   R is alkyl of 1 through 4 carbon atoms; with an o-phenylenediamine of the following formula: ##STR28## where X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; in an aqueous acidic medium at a pH of 2.5 to 5 until the precipitation of a 2-benzimidazolecarbamic acid ester is complete, and recovering said 2-benzimidazolecarbamic acid ester from the reaction mixture.   
     
     
       8. The process of claim 7 at a temperature from 40° to 130° C. 
     
     
       9. A process for making a 2-benzimidazolecarbamic acid ester comprising reacting an alkyl cyanocarbamate salt of the following formula:   [HNR.sub.5 R.sub.6 R.sub.7 ] . [N(CN)CO.sub.2 R]     where   R 5  and R 6  are alkyl of 1 through 4 carbon atoms; and   R 7  is alkyl of 1 through 4 carbon atoms, or aralkyl of 7 through 12 carbon atoms;   R is alkyl of 1 through 4 carbon atoms; with an o-phenylenediamine of the following formula: ##STR29## where X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; in an aqueous acidic medium at a pH of 2.5 to 5 until the precipitation of a 2-benzimidazolecarbamic acid ester is complete, and recovering said 2-benzimidazolecarbamic acid ester from the reaction mixture.   
     
     
       10. The process of claim 9 at a temperature from 40° to 130° C. 
     
     
       11. A process for making a 2-benzimidazolecarbamic acid ester comprising reacting an alkyl cyanocarbamate salt of the following formula:   [NR.sub.1 R.sub.2 R.sub.3 R.sub.4 ] . [N(CN)CO.sub.2 R]     where   R 1 , r 2  and R 3  are alkyl of 1 through 4 carbon atoms; and   R 4  is alkyl of 1 through 4 carbon atoms or aralkyl of 7 through 12 carbon atoms;   R is alkyl of 1 through 4 carbon atoms; with an o-phenylenediamine of the following formula: ##STR30## where X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; in an aqueous acidic medium at a pH of 2.5 to 5 until the precipitation of a 2-benzimidazolecarbamic acid ester is complete, and recovering said 2-benzimidazolecarbamic acid ester from the reaction mixture.   
     
     
       12. The process of claim 11 at a temperature from 40° to 130° C. 
     
     
       13. A process for making a 2-benzimidazolecarbamic acid ester comprising reacting an alkyl cyanocarbamate salt of the following formula:   [HN(R.sub.8).sub.3 ] . [N(CN)CO.sub.2 R]     where   N(r 8 ) 3  is triethanolamine or triethylenediamine;   R is alkyl of 1 through 4 carbon atoms; with an o-phenylenediamine of the following formula: ##STR31## where X is hydrogen, halogen, nitro or alkyl of 1 through 4 carbon atoms; in an aqueous acidic medium at a pH of 2.5 to 5 until the precipitation of a 2-benzimidazolecarbamic acid ester is complete, and recovering said 2-benzimidazolecarbamic acid ester from the reaction mixture.   
     
     
       14. The process of claim 13 at a temperature from 40° to 130° C.